An AC surface-discharge-type PDP is composed of a front substrate, formed with a plurality of display electrodes including scanning electrodes and sustain electrodes; and a back substrate, formed with a plurality of address electrodes orthogonal to the display electrodes. The front and back substrates are arranged facing each other so that they form a discharge space therebetween, their peripheries are sealed, and a discharge gas such as neon, xenon, or the like is encapsulated in the discharge space. The display electrode is covered with a dielectric layer, forming a protective layer thereon. The protective layer is generally formed with a material with a high anti-sputtering property such as magnesium oxide (MgO), protecting the dielectric layer from ion bombardment caused by discharge. In addition, each display electrode composes one line, forming a discharge cell where it crosses an address electrode.
In such a PDP, one field ( 1/60 second) for an image signal is composed of a plurality of subfields, each having a luminance weight. Each subfield has an address period, during which data is written by write discharge in a discharge cell to be lighted with each line scanned sequentially; and a sustain period, during which the discharge cell is lighted by discharge for the number of times corresponding to the luminance weight, in discharge cells where data has been written in the address period.
For displaying a television image, all the actions for each subfield must be completed within one field. Therefore, write discharge in each line needs to be completed in a shorter time as the number of lines (scan lines) increases with moving to finer-resolution of discharge cells. In other words, high-speed drive is required in an address period by narrowing the width of pulses applied to a scanning electrode and address electrode for generating write discharge. However, due to “discharge delay,” which means discharge occurs a certain time delayed after a pulse rises, the discharge completes while pulses are applied with a low probability, for the above-mentioned high-speed drive. Consequently, writing data to a discharge cell to be lighted sometimes fails, causing a lighting defect to lose display quality.
As the main factor that causes the above-mentioned discharge delay, primary electrons to trigger discharge are presumably becoming hard to be emitted into the discharge space from the protective layer. Therefore, display quality is expected to be improved by examining the protective layer.
In order to improve the behavior of such electron emission from a protective layer, a case is disclosed, for example, in the patent gazette (Publication No. 10-334809), where secondary electrons emit more increasingly by including silicon (Si) in a protective layer made of MgO, raising the display quality.
Meanwhile, if Si is included in a protective layer made of MgO, the capacity of electron emission largely fluctuates according to the temperature of the protective layer, and so does the discharge delay time. Consequently, the quality of image display changes according to the environmental temperature when a PDP is practically used.
In order to solve such a problem, the present invention aims at implementing a high-speed response for generating discharge to an applied voltage by shortening the discharge delay time, as well as at suppressing the change in the discharge delay time according to temperature.